The widespread availability of camera phones having a camera function in recent years has increased the opportunities for users to photograph various kinds of photographic subjects. For example, a photographic subject at a distance from the camera lens, such as a friend or scenery, is photographed (normal snapshot) or a photographic subject at a close distance from the camera lens, such as a bus time schedule or flower petals, is photographed (close-up photography).
For close-up photography (macro photography), the camera lens needs to be positioned slightly closer to the photographic subject than for a normal snap shot. Therefore, a photographing lens system of this kind is equipped with a drive mechanism that drives the lens to be displaced in the optical axis direction; by switching a switch, the drive mechanism is driven to move the lens in the optical axis direction (see Patent Reference 1, for example).
The lens driving apparatus disclosed in Patent Reference 1 comprises a lens barrel equipped with lenses, a movable body for retaining the lens barrel and a support body that supports the movable body to move in the optical axis direction of the lenses; a drive magnet is arranged to the movable body and a drive coil and two magnetic pieces (yokes) are arranged to the support body. The movable body is held at the closer of the two magnetic pieces by using magnetic attraction between the drive magnet and the magnetic piece when electrification to the drive coil is halted.
According to Patent Reference 1, the movable body moves in the direction of the optical axis of the lens in a limited, predetermined range. More specifically described, as disclosed in Patent Reference 1, the movable body (lens barrel) makes contact with a projection edge formed inwardly at the rear end of a first case division. Therefore, the lens barrel will not further move toward the rear end. In general, a guide mechanism configured with a recess (or a protrusion) which engages with a protrusion (or a recess) of the lens barrel is formed around the projection edge. This is provided for forming a rotating-prevention structure that prevents the lens barrel from rotating when the lens movable body receives shocks or vibrations.
Also, in the above-mentioned lens driving apparatus, the movable body and the support body are connected to each other via spring members; one has been proposed as the spring member, in which an outside joint portion is connected to the support member, an annular frame-type inside joint portion is connected to the movable body and an arm portion connects the outside joint portion to the inside joint portion, and the arm portion meanders back and forth outside the movable body (see Patent References 2, 3)
The arm portion demonstrates spring property in the spring member between the outside joint portion and the inside joint portion; therefore, when the movable body is moved in the optical axis direction, the spring member regulates the moving amount of the movable body in the optical axis direction. Mobile apparatuses frequently receive vibrations and shocks because they are mobile; such vibrations and shocks are absorbed by the arm portion.    [Patent Reference 1] Japanese Unexamined Patent Application (Tokkai) NO. 2005-37865 (FIG. 2)    [Patent Reference 2] Japanese Unexamined Patent Application (Tokkai) NO. 2006-201525    [Patent Reference 3] Japanese Unexamined Patent Application (Tokkai) NO. 2006-227103
Problems of the Prior Art. However, the guide mechanism disclosed in the above-mentioned Patent Reference 1 is formed in a complicated shape. Therefore, the manufacturing process of the lens driving apparatus becomes complicated, increasing time and cost of manufacturing. Also, as described above, the movable body (lens barrel) is regulated in its moving range by the projection edge located in the vicinity of the optical axis; when the lens body hits the projection edge, wear powder may be produced and may adhere to the sensor surface (such as a filter of a photo device) arranged in the vicinity. If wear powder adheres to the sensor surface, the photographed images become blurred, thus degrading the performance of the lens driving apparatus.
The present disclosure proposes a spring member having a shape which allows the spring member to be flexibly used even in a rectangular parallel-piped lens driving apparatus. In order to realize the proposal, the spring member is arranged in a small area between the frame portion of the support body whose cross-section perpendicular to the optical axis is a quadrangle barrel shape and the movable body whose outside circumference is circular cylindrical. However, when the spring member disclosed in Patent Reference 1, 2 is used in the lens driving apparatus having such a configuration, there is not much freedom in designing the arm portion and only an insufficient spring property can be demonstrated. Also, when the movable body in the lens driving apparatus receives a strong shock from being dropped and moves abruptly in the direction perpendicular to the optical axis direction (the left-right direction or circumferential direction) or the diagonal direction (the tilt direction) with respect to the optical axis direction, a conventional spring member may easily suffer from plastic deformation or breaking, causing problems such as poor stroke in the lens driving apparatus.
Considering the above problems, at least an embodiment of the present invention provides a lens driving apparatus that can prevent problems even when receiving a strong shock such as the impact of being dropped.
Also, at least an embodiment of the present invention may provide a lens driving apparatus that can prevent the problem in particular of wear powder adhering to a sensor surface even when the device receives a strong shock such as the impact of being dropped.
Further, at least an embodiment of the present invention may provide a lens driving apparatus that can prevent problems such as plastic deformation and breaking of the spring member when the device receives a strong shock such as the impact of being dropped.